In a submarine optical communication system, optical signals communicated through the submarine optical fiber cable become attenuated over the length of the cable, which may stretch thousands of miles. To compensate for this signal attenuation, optical repeaters are strategically positioned along the length of the cable.
FIG. 1 illustrates a perspective view of a typical submarine optical repeater 10 having a cylindrical housing 12. A first submarine optical cable 16 enters repeater 10 at first end cover 14 and connects to first internal optical cable 18, which, in turn, connects to an optical repeater assembly 20. Optical repeater assembly 20 typically includes at least the following items (not shown in FIG. 1): optical components, connecting optical fibers, electronic circuits, and connecting wiring. Optical repeater assembly 20 connects via a second internal optical cable 19 to a second submarine optical cable 17, which exits repeater 10 at second end cover 15.
Typically, the optical fibers found within optical repeaters are circular in cross-section, and are constructed of glass surrounded by a protective jacket that is thicker than the glass. For example, a typical glass fiber ("glass fiber", "bare fiber", or "unjacketed fiber") can have an outer diameter of approximately 0.010 inches, and a typical jacketed fiber can have an outer diameter of approximately 0.040 to 0.060 inches.
The glass fiber is fragile. Because even microscopic damage to the glass fiber can adversely affect the reliability of the optical repeater (and, as a result, the reliability of the entire submarine optical fiber cable system), great efforts are normally taken to protect the glass fiber from damage. Generally, the likelihood of damage to the glass fiber can be reduced by ensuring that any curvature in the glass fiber meets or exceeds the minimum bending radius of the glass fiber. However, the minimum bending radius of the glass fiber is a function of the expected life of the glass fiber. For example, when at least a 25-year life is expected, the glass fiber typically has a minimum bending radius of approximately 1 inch. This is referred to as the reliability-adjusted minimum bending radius of the glass fiber, because meeting or exceeding this value provides acceptable reliability from bending damage during the expected life of the glass fiber.
Typically, the optical components found within optical repeaters are manufactured with a segment of optical fiber attached at each end and cut to a specified length. Each fiber segment contains a jacketed portion of specified length located adjacent to the optical component, and a bare portion of specified length extending from the opposite end of the jacketed portion. The bare portion is spliced into the bare portion of another segment in the repeater's optical circuit. Creating these splices can be a complicated task, requiring substantial lengths of bare fiber on each side of the splice. Optimally however, the repeater is designed to be as space-efficient as possible, thereby minimizing its production, storage, shipping, and installation costs. Thus, it is desirable to store each optical fiber segment in the most space-efficient manner possible.
FIG. 2 illustrates a perspective view of a known fiber storage device that can be located within, for example, a submarine optical repeater or branching unit. Tray 42 includes generally circular portal spool 44 which is surrounded by generally square portal well 48. The square portal well includes a fiber portal 68. Tray 42 also includes generally circular storage spool 46 which is surrounded by generally square storage well 50. Optical device 54 is mounted to tray 42 in optical cavity 52 which is connected to storage well 50 by cavity-to-storage channel 58 and by storage-to-cavity channel 64. Optical cavity 52 is connected to portal well 58 by portal-to-cavity channel 72 and cavity-to-portal channel 66.
Optical device 54 is connected to jacketed storage fiber 56 at the end of optical device 54 nearest storage well 50. Just inside storage well 50, jacketed storage fiber 56 connects to bare storage fiber 59. The end of bare storage fiber 59 is spliced to the end of bare connecting fiber 60 at splice 74. Bare connecting fiber 60 extends from splice 74 to jacketed connecting fiber 62 which., in turn, extends through storage-to-cavity channel 64, through optical cavity 52, through device-to-portal cavity 66, and into portal well 48. Within portal well 48, jacketed connecting fiber 62 wraps around portal spool 44 and exits at portal 68.
Jacketed connecting fiber 70 exits from the opposite end of optical device 54 and extends through portal-to-cavity channel 72, and into portal well 48, where it wraps around portal spool 44 and exits at portal 68. Spools 44 and 46 are designed with a radius greater than or equal to the reliability-adjusted minimum bending radius of the bare portion of fibers 56 and 60.
Although not shown, tray 42 can define more than one optical cavity and accompanying channels. In that situation, each additional optical fiber of any additionally mounted optical devices is routed and stored similarly to fibers 56, 59, 60, 62, and 70, i.e., in the channels connected to their respective optical cavity and around their respective spools. When more than one fiber is to be spooled around either spool 44 or 46, each additional fiber is wrapped around the spool generally above the preceding fibers, thereby forming a stack of spooled fibers.
Absent a late-stage design modification, jacketed fibers are generally not allowed to substantially intrude into the well where bare fiber is spooled, because such an intrusion can cause a jacketed fiber to press against or be spooled with a bare fiber. This is disadvantageous because the diameter of the jacketed fiber is much smaller than the reliability-adjusted minimum bending radius of the bare fiber. Thus, if the bare fiber is bent against the jacketed fiber, a violation of the minimum bending radius of the bare fiber can result, potentially causing unacceptable mechanical stresses in the bare fiber. Such a situation is particularly likely when a number of spooled bare fibers are stacked on a spool, and each fiber must be pushed down into the well to make room for the successive fibers, the pushing action thereby greatly increasing the forces bending the bare fiber around the intruding jacketed fiber.
When intrusion is unavoidable, the jacketed portion may only extend into the well when the well has sufficient space to prevent the intruding jacketed portion from contacting the spooled bare portion. This means that the jacketed portion may typically intrude into the well by no more than about 1 inch. If the jacketed portion will intrude by more than about 1 inch, the tray design, or more typically the optical component design, should be modified to avoid damage to the bare fibers. However, when design changes substantially affect fiber portion lengths, other difficulties can ensue.
Changes in the length of the bare fiber portion can sometimes be accommodated by adjusting the amount of bare fiber wound around the spool, or adjusting how tightly the bare fiber is wound around the spool. However, an increase of more than 1 inch in the length of the jacketed fiber portion typically requires a change to the optical component's manufacturing specification, because, as discussed previously, such an increase could cause the jacketed fiber to intrude excessively into the bare fiber storage area. Likewise, a decrease in the jacketed fiber's length could cause the bare fiber to be stored, unprotected, in a fiber channel, where it could be scratched by contact with the channel, or could be bent against an edge of the channel or another jacketed fiber.
As previously discussed, these types of situations could expose the bare fiber, and potentially the entire submarine optical fiber cable system, to unacceptable damage. Thus, changes in the length of the jacketed fiber portion often require a change to the optical component's manufacturing specification. Such specification changes are typically very costly, particularly if initiated after the manufacturer has begun producing the optical component.
Thus, there is a need for a device that allows jacketed fiber and bare fiber to be stored in a protective, space-efficient, and separate manner, and that accommodates substantial changes to the length of jacketed fiber after the storage tray has been designed, and particularly after optical components have been specified and ordered.
However, this is not the only disadvantage to the known fiber storage devices. Accessing a bare fiber stored in the known fiber storage devices can be challenging. For example, assume that four bare fibers are spooled in a stacked manner around the same spool, and that access to the bottom-most fiber in the stack is required. However, because the well is very compact, it is difficult for the assembler's fingers to reach therein, particularly when the well is more than a fraction of an inch in depth, as it typically is. Also, because the bare fibers are very small in diameter, each bare fiber can be very difficult to grab. Thus, a pointed stick is typically used to select a bare fiber and slide it to the top of well where it can be grasped. Then, the bare fiber is unspooled and moved out of the way, and the process repeated until the desired fiber is obtained. However, using a stick in this manner is a clumsy endeavor, and can cause scratches or other mechanical damage to the bare fibers. Thus, there is a need to provide an improved device for moving each spooled fiber within a fiber storage device.
There are also disadvantages with the known assembly for segregating bare fibers. To facilitate segregating two or more bare fibers that have been wrapped around a spool and within a well, a multi-envelope assembly is typically assembled around the spool and within the well. A known multi-envelope assembly includes a single envelope bottom, a plurality of envelope liners, a plurality of envelope tops, and optionally, one or more comer protectors.
FIG. 3 illustrates a top view of envelope bottom 100. Envelope bottom 100 is a single layer of white opaque fibrous paper, such as that bearing the TYVEK.RTM. brand. Envelope bottom 100 has foldable scaling flaps 102 along three of its four outer sides. When sealing flaps 102 are folded upwards, envelope bottom 100 is generally square in shape, thereby corresponding to the generally square walls of the well. To provide a partial sealing flap yet allow a fiber to enter and exit, along the fourth side of envelope bottom 100 are three foldable side tabs 108. Corresponding to the generally circular spool, bottom 100 has a generally circular opening 104, into which extend four, foldable short inner tabs 106, and four, foldable long inner tabs 107 which are equally spaced circumferentially. Short inner tabs 106 are located along imaginary diagonal lines that connect the corners of bottom 100. Long inner tabs 107 are located along imaginary lines that perpendicularly bisect and connect the sides of bottom 100.
Envelope bottom 100 fits snugly around the spool and within the well, such that sealing flaps 102 and side tabs 108 fold up along the walls of the well, and inner tabs 106 and 107 fold up along the outer circumference of the spool.
A top view of envelope liner 110 is illustrated in FIG. 4. Like envelope bottom 100, envelope liner 110 is a single layer of white opaque fibrous paper, such as that bearing the TYVEK.RTM. brand. Moreover, envelope liner 110 is nearly identical in shape and size to envelope bottom 100, except that liner 110 does not have any tabs corresponding to the four, foldable long inner tabs 107, and only has two side tabs rather than the three of envelope bottom 100. Thus, envelope liner 110 has foldable sealing flaps 112 along three sides, and two foldable side tabs 118 along its fourth side. Corresponding to the spool, liner 110 also includes a roughly circular opening 114, into which extend four, foldable inner tabs 116 that are equally spaced circumferentially around opening 114.
Envelope liner 110 also fits snugly around the spool, around the long inner tabs of bottom 100, and within the well, such that flaps 112 and side tabs 118 fold up along the walls of the well, and inner tabs 116 fold up along the outer circumference of the spool.
FIG. 5 provides a top view of envelope top 120. Envelope top 120 is approximately square, with a circular opening 124 that corresponds to the spool. Like envelope bottom 100 and envelope liner 110, envelope top 120 is constructed of a white opaque fibrous paper, such as that bearing the TYVEK.RTM. brand. However, envelope top 120 is constructed of a dual-layer paper having a bottom layer coated with an adhesive, and a top layer releasably joined via that adhesive to the bottom layer.
Along three sides, envelope top 120 has pre-perforated flap scaling zones 122, the top layer of which can be removed leaving corresponding adhesive zones for receiving sealing flaps 112 from liner 110, or sealing flaps 102 from bottom 100. Along its fourth side, envelope top 120 has pre-perforated side tab sealing zones 128, the top layer of which can be removed leaving corresponding adhesive zones for receiving side tabs 118 from liner 110, or side tabs 108 from bottom 100. Evenly spaced around circular edge 124 are four, pre-perforated short inner tab sealing zones 126, the top layer of which can be removed leaving corresponding adhesive sealing zones for receiving inner tabs 116 from liner 110, or inner tabs 106 from bottom 100.
Referring to FIG. 6, a corner protector 130 is illustrated. Corner protector 130 serves to protect the spooled bare fiber within a well when the jacketed portion of the fiber extends slightly (less than 1 inch) into the well. Corner protector 130 is placed over the comer nearest the protruding jacketed fiber. Folding flap 132 folds alongside the wall of the well. Arcuate edge 134 is placed adjacent to the spool.
FIG. 7 illustrates a cross-sectional view of a known multi-envelope assembly 90. Referring to FIG. 7, multi-envelope assembly 90 is adapted to be used on a fiber storage tray 80 having an elongated square well 82 surrounding all elongated circular spool 84. Multi-envelope assembly 90 is constructed of a single base envelope 92, followed by a plurality of standard envelopes 94. Base envelope 92 is constructed using a single envelope bottom 100 and a single envelope top 120. Standard envelope 94 is constructed using a single envelope liner 110 and a single envelope top 120. Long inner tabs 107 of envelope bottom 100 tie base envelope 92 to a plurality of standard envelopes 94 to form multi-envelope assembly 90.
More specifically, multi-envelope assembly 90 is assembled as follows:
1) obtain envelope bottom 100 and fold upwards each of flaps 102, side tabs 108 (not shown in FIG. 7), short inner tabs 106, and long inner tabs 107; PA1 2) place envelope bottom 100 around spool 84 and within well 82, such that long inner tabs 107 extend along the outer wall of spool 84; PA1 3) spool a first fiber 88 around spool 84 and within well 82; PA1 4) obtain envelope top 120 and remove the top layer covering each of flap sealing zones 122, side tab sealing zones 128 (not shown in FIG. 7), and short inner tab sealing zones 126; PA1 5) place envelope top 120 over spool 84 such that side tab sealing zones 128 (not shown in FIG. 7) align with side tabs 108 (not shown in FIG. 7) of bottom 100; PA1 6) place envelope top 120 around spool 84 and within well 82, such that long inner tabs 107 extend along the outer wall of spool 84 and above envelope top 120; PA1 7) gently fold and press the each of the following elements of envelope bottom 100 onto their respective sealing zones of envelope top 120 to partially seal base envelope 92: PA1 8) obtain an envelope liner 110 and fold upwards each of flaps 112, side tabs 118 (not shown in FIG. 7), and short inner tabs 116; PA1 9) place envelope liner 110 around spool 84 and within well 82, such that long inner tabs 107 of bottom 100 continue to extend along the outer wall of spool 84; PA1 10) spool another fiber 88 around spool 84 and within well 82; PA1 11) obtain envelope top 120 and remove the top layer covering each of flap sealing zones 122, side tab sealing zones 128 (not shown in FIG. 7), and short inner tab sealing zones 126; PA1 12) place envelope top 120 over spool 84 such that side tab scaling zones 128 (not shown in FIG. 7) align with side tabs 118 (not shown in FIG. 7) of liner 110; PA1 13) place envelope top 120 around spool 84 and within well 82, such that long inner tabs 107 of envelope bottom 100 continue to extend along the outer wall of spool 84 and above envelope top 120; PA1 14) gently fold and press the each of the following elements of envelope liner 110 onto their respective sealing zones of envelope top 120 to partially seal standard envelope 94: PA1 15) fold long inner tabs 107 of bottom 100 over top 120 and away from spool 84; PA1 16) install a cover (not shown) over fiber storage tray 80.
sealing flaps 102 onto flap sealing zones 122; PA2 side tabs 108 (not shown in FIG. 7) onto side tab sealing zones 128 (not shown in FIG. 7); and PA2 inner short tabs 106 onto short inner tab sealing zones 126. PA2 flaps 112 onto flap sealing zones 122; PA2 side tabs 118 (not shown in FIG. 7) onto side tab sealing zones 128 (not shown in FIG. 7); and PA2 inner short tabs 116 onto short inner tab sealing zones 126.
At this point, base envelope 92 has been assembled. Next, a standard envelope 94 is constructed and attached to base envelope 92 as follows:
Steps 8 through 14 are repeated as necessary to construct additional standard envelopes 94 to accommodate all the bare fibers 88. Once the last standard envelope 94 has been assembled, the following steps are taken to finalize multi-envelope assembly 90:
The adhesion of flaps 102, side tabs 108 (not shown in FIG. 7), and inner tabs 106 to their respective sealing zones seals bottom 100 to top 120, thereby forming base envelope 92. Likewise, the adhesion of flaps 112, side tabs 118 (not shown in FIG. 7), and inner tabs 116 to their respective sealing zones seals liner 110 to top 120, thereby forming standard envelope 94. The folding of long inner tabs 107 over top 120 and away from spool 84 assists in preventing any fiber 88 from laying across the top of spool 84, and links base envelope 92 and each standard envelope 94 into multi-envelope assembly 90.
However, there are numerous disadvantages to multi-envelope assembly 90. The pressing required to adhere flaps and tabs to the sealing zones of envelope top 120 can cause unacceptable forces to be applied to the fibers and splices contained below. Moreover, the folding of flaps and tabs, and the pressing required to adhere flaps and tabs is very time-consuming. Furthermore, the need for flaps extending along nearly the entirety of the length of each edge of both envelope bottom 100 and envelope liner 110 strongly militates in favor of the well being a square, or at most a regular polygon having a relatively small number of sides. However, a square well can limit the well entry locations and angles for a fiber or its channel, thus substantially constraining the geometry of the storage tray.
There are additional disadvantages to multi-envelope assembly 90. For example, accessing a bare fiber stored in multi-envelope assembly 90 can be challenging and risky to the integrity of the fiber. Once the desired envelope has been removed from the well, each of the flaps and tabs must be pried free from envelope top 120, potentially exposing the bare fiber and the splice to unacceptably high mechanical stresses. Moreover, because multi-envelope assembly 90 is opaque, determining the location of the bare fiber and the splice is particularly difficult, thus increasing the difficulty of avoiding the application of prying stresses to the bare fiber or splice.